A Proton That Is Being Accelerated Travels Along Arcs of a Circle

Multiple Choice

A proton that is being accelerated travels along arcs of a circle through the magnetic fields of a cyclotron.Near the beginning of its path through the cyclotron,the speed of the proton is slow and the radii of the arcs are small.Near the end of its path,the radii are large and the speed is c/3,so the motion of the particle must be treated relativistically.What must the ratio of the average magnetic field at the edge of the cyclotron to that at the center be to compensate for the relativistic momentum of the proton? HINT: The cyclotron frequency f = qB/2 $\pi$ m must remain constant for the proton throughout its path.

A) 0.94
B) 0.33
C) 1.3
D) 1.06
E) 1.7